KAZOO-3840 allow pre-loaded routes for grandstream

kamailio/default.cfg

@@ -517,9 +517,15 @@ route[PREPARE_INITIAL_REQUESTS]
     }
 
     if (loose_route()) {
-        xlog("L_WARN", "$ci|end|denying initial request with route-set");
-        sl_send_reply("403", "No pre-loaded routes");
-        exit();
+        $xavp(regcfg=>match_received) = $su;
+        $xavp(regcfg[0]=>match_contact) = $(ct{nameaddr.uri});
+        if(registered("location", "$rz:$Au", 6) == 1 && ($ua =~ "Grandstream") ) {
+           xlog("L_INFO", "$ci|chk|allowing initial route-set for $Au");
+        } else {
+           xlog("L_WARN", "$ci|end|denying initial request with route-set");
+           sl_send_reply("403", "No pre-loaded routes");
+           exit();
+        }
     }
 
     if (!is_method("MESSAGE")) {